Hi from Just Answer. Thanks for asking for me.
Payouts from MLP are often part income, part return of basis. Only the income portion could get UBTI treatment, and then only if the total UBTI was $1,000 or more.
REIT income is normally a higher portion of income, and little to no return of capital, and there are more opportunities to receive UBTI from a REIT. The same test holds for taxability.
These same rules apply to a Roth IRA, and yes, it can have taxable income from UBTI.
Thanks again for asking for me, and thanks from Just Answer.